


In Every Possible Universe

by aunnoo



Category: Haikyuu!!
Genre: Anastasia AU, Canon Compliant, Drabble Collection, Fluff, M/M, More Fluff, Slice of Life, Soulmate AU, alternative universe, collection from tumblr, i just want my boys to be happy
Language: English
Status: In-Progress
Published: 2016-08-14
Updated: 2016-10-22
Packaged: 2018-08-08 17:12:38
Rating: General Audiences
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 4
Words: 3,212
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/7766374
Author URL: https://archiveofourown.org/users/aunnoo/pseuds/aunnoo
Summary: <blockquote class="userstuff">
              <p>They met at birth in this life, this universe. They grew up. They laugh and cry, fight against each other then together against the world. One of them fell in love before he knew it and it's not surprised the other did, too. </p><p>It's still a wonder. </p><p>A wonder they'd do anything to make happened, in every possible universe.</p>
            </blockquote>





	1. Engagement Shtick

**Author's Note:**

> Headcanon of iwaoi childhood engagement shtick -- asked by anon

When they are four, Oikawa learns that marriage is between two people who want to be together forever from TV (a romcom movie his sister’s watching).

The next day he asks Iwaizumi if _Hajime-chan_ would want to be with him forever. Iwaizumi says yes.

“ _Of course. We are best friends_.”

That same day, Mrs. Oikawa is greeted with her two favorite boys, holding hands, at the Oikawa doorstep and her son declaring proudly that he and Hajime-chan want to get married.

Mrs. Oikawa makes extra agedashi tofu for dinner as a welcome gift for her future son-in-law.

Iwaizumi, at age four, figures that marrying Oikawa Tooru isn’t a bad thing.  
  


* * *

  
When they are six, Iwaizumi learns that marrying someone means you vow to take care of that person and bring happiness to their life from his father.

The next time Oikawa insists to tag along Iwaizumi’s bug hunting and once again scrapes his knees and is on the verge of crying, Iwaizumi covers every wound with the nyon-colored bandages Oikawa has collected (“ _Did you get hurt on purpose just to use them?_ ”) before taping one around Oikawa’s middle finger carefully.

“ _You don’t need to cry, I am taking care of the wound, just like I promise to marry you, right?_ ”

Oikawa bursts into tears right after and cries again when his mother tries to convince him to take off the bandage ring a week later, telling him that wedding rings are supposed to wear on ‘the fourth finger’ not the third.  
  


* * *

  
When they are nine, they learns that marriage costs a lot of money from Oikawa’s sister.

Iwaizumi brings over a huge glass jar the next time they have a sleep-over and suggests that if they are going to get married, they should probably start saving money.

They put all their pocket money in it and discuss what they are going to have on their wedding. The list contains a three-layered cake (one layer of chocolate, one strawberry and one cream butter with pudding because it’s impossible to choose just one), a dog as their minister, and alien and Godzilla stickers for the invitations.

The jar is emptied before it is half-filled for a new volleyball after they join the school volleyball club.  
  


* * *

  
When they are twenty-three, after they first move in together, Iwaizumi places a glass jar on the shoe cabinet in their hallway.

Oikawa never asks what it’s for but he makes a new habit of only paying in paper bills and putting all the changed coins in the jar.

A year later, they carry ten jars of coins to the bank and take the check to get a pair of platinum rings.

The smile on Oikawa’s face when Iwaizumi slides the ring onto his ‘fourth finger’ rivals all the bright things ever existed in the universe.

They are twenty-four and they finally, _finally_ understand that marriage is about promises, promises to stay together, to take care of themselves and the other, to laugh and fight and laugh again, and to fall in love with that same person for a million times and more.

Iwaizumi, at age twenty-four, decides marrying Oikawa Tooru is the best thing.

**Notes for the Chapter:**

> Maybe after 100 drabbles I could learn how to write longer things?  
> Writing is sure hard but please enjoy some iwaoi fluff!
> 
> Feel free to drop by and talk to me about my boys!  
> tumblr: aunnoo-iwaoi-headcanon.tumblr.com (main blog: aunnoo.tumblr.com)


	2. Birthday Surprise

**Summary for the Chapter:**

> Headcanon of Oikawa organising surprise party for Iwa's birthday -- asked by lyly1805 
> 
> The drabble is based on two facts:  
> \- When Oikawa plans, he likes to plan everything.  
> \- Oikawa get excited over surprises and it shows on his behaviors. (So Iwaizumi can always tell.)

When it comes to Iwaizumi, it seems impossible for Oikawa to surprise him.

Surprise gift, failed. Surprise party, failed. Surprise attack from the corner, failed. Even Oikawa’s accidental confession on their high school graduation day (which has surprised even himself,) didn’t manage to move Iwaizumi. 

_“I know, idiot,” Iwaizumi has said, his ears pink against his sun-kissed skin as he brushed a loose lock of fringe away from Oikawa’s eyes. “Don’t look about to cry as if I were to reject you.”_

But Oikawa is anything but determined, and seeing back, despite all the failed attempts, he always gets to bring a smile to his best friend’s lips. Either it’s teasing or amusing or genuinely happy, it should be counted as success. 

Now at age twenty five, as a professional volleyball player who is known for his sharp mind of calculating attacks, Oikawa deems himself ready to surprise the  _unmoving stone_  of his stubbornly perfect lover.   


* * *

  
**Time: 06/10  00:00**  
**To: Iwa-chan Hajime  
** **Subject: Happy birthday Iwa-chan!!!!!!!**

Happy 26th birthday Iwa-chan!!! (σ◉∀◉)σ *:･ﾟ✧ ( -`‸´- )  
I am here to grant you your first birthday wish. Aren’t I the best boyfriend ever?  
Come home quick and give me some love I deserve!!  
Have a nice sleep and a nice trip tomorrow. ( *ˊ  3 ˋ*)♡ㄘゅ

  
**Time: 06/10  09:34**  
**From: Iwa-chan Hajime**  
**Subject: Re: Happy birthday Iwa-chan!!!!!!!**

Aren’t I the one getting all the love today since it’s my birthday, best boyfriend ever?  
Anyway, there’s an impromptu meeting this afternoon, but I’d be able to catch the 15:20 train back.  
Would let you know if I could make dinner.  
Love you.  


* * *

  
It’s like Fate has a personal problem with him wanting to surprise his boyfriend.

Nothing goes right the moment Oikawa gets off the bed.

He trips over a blanket and falls right on the face. 

With a nosebleed, he finds his usually  _naturally_  perfect hair choose this day to be rebellious, with a lock standing up funnily on the side and refusing to be tamed.

He visits five flower shops and sees no hydrangea with the perfect shade of bluish purple resembling the ones he and Iwaizumi has seen during their trip to Karakuma during their last year in university in Tokyo. 

He pokes the purple ( _purple_  with only a little hint of blue) hydrangea sitting on their dining table as he eyes his phone. He wants to call Iwaizumi but he doesn’t trust his frustrated self (or himself in general) can withhold the information of Iwaizumi’s surprise party.

The last straw comes in the form of a text.

**Time: 06/10  15:34**  
**From: Iwa-chan Hajime**  
**Subject: No subject**

Missed the 15:20 train but there’s another one in an hour.  
You can eat first if you’re hungry.

  
Oikawa lets Kuroo ringing his doorbell for 5 whole minutes before he gets up and gets the door.  


* * *

  
Oikawa decides he’s never going to try and surprise Iwaizumi again.

“Tetsu-chan, why isn’t anyone here yet?” 

“Well,” Kuroo shrugs, nonchalant. “Traffic and stuff I guess. Isn’t Iwaizumi going to be a bit late anyway?”

“Yes, but everything should be ready before… Ushiwaka-chan, did you just put the cake in the oven?”

“Yes?” Ushijima replies.

“Please tell me you can finish it in less than thirty minutes,” Oikawa says, rubbing his temple.

“Well, it takes thirty minute to bake. The cake is big.” 

Oikawa sighs. “At least tell me Akaashi is on his way to pick up Iwa-chan.”

“Oh sure,” Kuroo says, grinning. “Akaashi isn’t Iwaizumi favorite kouhai for nothing. Hey, don’t give me the look, I am not the one stealing your man’s affection.”

“I should’ve sent you to pick up Iwa-chan instead,” Oikawa says with a piercing glare.  

Kuroo’s grin only grows wider. “Oh please, Iwaizumi would know what you’re planning the moment he sees me on the platform.”  


* * *

  
The bell rings right after Ushijima finishes the icing and is about to ask Oikawa what words he’d like to put on the cake. 

“Oikawa, we are here!” Hanamaki, who is supposed to have arrived 30 minutes ago, announces loudly,  _shamelessly_ , outside the door. 

“Makki,” Oikawa says, striding towards the door. “I swear to god, you should’ve been here like-” he throws open the door- “30 min-” he pauses. 

“ _Hajime!?_ ”

There, standing in the entrance of their hallway and surrounded by their friends, is Iwaizumi Hajime, suited-up, hair half-slicked back, with two roses in hand. 

“Hey, Tooru,” Iwaizumi greets, smiling brightly with one canine teeth showing and Oikawa is so so  _weak_ for this man.

“Iwa-chan,” Oikawa whines, shoulders dropping dramatically. “You shouldn’t crash your own surprise party.”

Iwaizumi laughs and Oikawa can’t help the smile tugging at his lips. “I didn’t mean to crash it. It’s just you’ve managed to invite all our friends here. I don’t want to miss the chance.”

“Miss the chance of-” Oikawa pauses the second time that night as Iwaizumi drops down to one knee and holds out the roses, a ring dangling from the teal ribbons tied around the stems. 

There’s that nostalgic pink in Iwaizumi’s ears as he stares up at Oikawa. 

“Oikawa,” Iwaizumi breathes. “Oikawa Tooru, would you marry me?”

Oikawa only stares. A second, two second, then, “no.”

Collective intakes of shock echo the hallway. 

Iwaizumi looks completely lost and Oikawa can’t hold back the sobs tearing through his throat as he tackles Iwaizumi down with a crashing hug. 

“Hajime,” Oikawa cries into the crook of his lover’s neck, feeling Iwaizumi’ arms circling his waist. “How can you be surprised by  _that_? You even know this surprise party when you aren’t in the city. Y-you are so mean to me.”

Iwaizumi chokes out a laugh. “Considering your current answer to my proposal is still an no. You are the one being mean here.”

“Yes,” Oikawa says, lifting himself up so he can look straight into Iwaizumi’s green  _green_  eyes. “Yes. Yes. _Yes_. Please marry me, Hajime.”

Iwaizumi beams, eyes crinkling.  _Sparkling_. “With pleasure.”

Someone coughs before Oikawa can gets himself a kiss. “Congratulation, Iwaizumi-san, Oikawa-san. But can you move so people could get in the apartment?”

“I don’t mind stepping over them. I’ve wanted to do that for a while.”

“Makki,” Oikawa exclaims, exasperatedly. 

He scrambles up, pulling Iwaizumi up with him and back against the wall as their friends chat and walk into their apartment like the proposal has never happened. 

“Good friends we have, huh,” Iwaizumi says, shoulder nudging Oikawa’s. 

“Yeah,” Oikawa replies, looking down at Iwaizumi. “But I got you as my best friend.”

“Yeah,” Iwaizumi echos, warm fingers intertwining longer ones. “And I got you.”

They lean in at the same time and Oikawa smiles as their lips met in the middle. 

**“Happy birthday, Hajime.”**

**Notes for the Chapter:**

> Don't we all need a bit of iwaoi fluff?
> 
> tumblr: aunnoo-iwaoi-headcanon.tumblr.com (main blog: aunnoo.tumblr.com)


	3. Anastasia AU

**Summary for the Chapter:**

> Anastasia AU for all my movie crossover need. 
> 
> The train scene suggested by reminscees. (A character study of the boys in this AU.)

The suitcase is heavy and Oikawa gives an extra push to get it over the overhead storage.

He is about to take the window seat across Iwa before hurriedly backs off from the growling dog that occupies said seat. 

“The manner,” Oikawa mumbles, reluctantly flopping himself into the seat next to Iwa. He takes a quick peek at the young man slouching in the seat, staring absentmindedly out the window while his hand fiddles with his necklace. “Just like his owner.”

Oikawa purses his lips and crosses his legs. His brows knit into a frown as he takes another glance at Iwa’s lounging figure and he can’t stop the reproach rolling off his tongue.

“You need to sit up straighter. And stop fiddling with that chain, it’s not royal-like, great grand duke Iwaizumi.”

Turning from the window, Iwa folds his arms (Oikawa eyes follows the movement of muscles under plain fabric) and tchs. “Like you know what a duke do or not do, your highness of fairy land.”

“I know I am gorgeous but please drop the honorific, Iwa-chan,” Oikawa smirks, tone teasing. “I am just trying to help here, okay?”

Rolling his eyes, Iwa straightens from the seat, head held high as he locks eyes with Oikawa’s. “Oikawa.”

“Yes,” Oikawa says.

“Do you think I’m royalty?” Iwa asks, nonchalant.

“Of course I do, Iwa-ch-”

“Then stop bossing me around and treat me like one,” Iwa cuts him off, smirking challengingly at a slack-jawed Oikawa. He flops back into the seat, this time with one leg propping on the other while his hands outright  _play_  with his necklace.

It takes another few seconds before Oikawa manages to close his mouth. He turns to Kuroo, mouthing incredulously, “ _Did you hear that?_ ”

Kuroo shrugs, flashing Oikawa a feline smile. “You know I find witty guys attractive.”

“Aren’t royalty supposed to be rich but dumb-  _ouch_!” Oikawa cries, hand reaching down to rub at where Iwa kicks in his calf. 

“You should just stop talking,” Kuroo suggests, casually flipping open his notepad and adding another tally under the name ‘Iwa’, bringing the number to 23 versus Oikawa’s 4.  
  


* * *

 

  
Oikawa sighs as Kuroo leaves the compartment, giving Oikawa one meaningfully look before closing the compartment door.

Iwa has retired to reading a book, free hand patting the dog that has moved itself into Iwa’s lap. Oikawa wonders again how Iwa can find a dog with such a rare (or more like a weird mix of black and yellow) patterns of fur. 

_It’s not even cute for a puppy_ , Oikawa thinks sourly. 

Oikawa takes a deep breath and lifts himself off the seat, changing in the one across Iwa. He leans forwards, trying to catch the other man’s eyes behind the book he’s holding stubbornly between them. 

Oikawa coughs. “Look, I know not everybody can be naturally charming-”

“Really?” Iwa says, lowering his book. “If this is how you attempt for an apology, you surely don’t know how to act charming.”

“W-what?” Oikawa chokes.

“Don’t worry,” Iwa says, raising his book to cover his eyes but Oikawa can see the little quirk in the other man’s lips below the book cover. “I accept your apology.”

“I-I was not apologizing,” Oikawa kicks himself for stuttering. “Why would I? I was just trying to say-”

Iwaizumi sighs and closes the book. “Can you stop being so… chatty? It’s annoying.”

“Rude!” Oikawa exclaims. “And to think of how much we’ve helped you.”

“Oh god,” Iwa throws his hands in the air, startling the dog in his lap. 

The dog awakes, grumbling, before it turns to Oikawa and lets out an discontented growl. 

“You- this-” Oikawa says, scandalized, before he crosses his arms and pouts, looking out the window. “Fine, bullying me into silence with your dog.”

“Good boy,” Iwa coos to the dog, giving it a good ruffle in the head. 

The dog nuzzles itself into a comfortable position and Iwa watches it slowly drift back to sleep. 

He raises his eyes at the still pouting man when the other remains uncharacteristically silent. Biting his lips, Iwa asks, voice a bit too small to be casual. “Do you think you’d miss it?”

“Miss what?” Oikawa rumbles, still looking out the window.

“Miss Russia,” Iwa clarifies and adds. “Miss home.”

“Russia is not my home,” Oikawa replies. “And it’s too cold to be missed.”

“So is Paris your home then?” Iwa asks. “Or you plan to make it yours?”

“No, I mean, I don’t know,” Oikawa says, turning toward Iwa with a frown. “What’s with this talk about home?”

Iwa shrinks back in his seat, more defensive than anything. “What, can’t I wonder what’s it like to have a home?”

“Then asks someone who  _cares_  to have one,” Oikawa snaps.

Neither of them speaks for a while and the silence is starting to make Oikawa uncomfortable. He squirms a little, feeling guilt rising inside his stomach. He’s about to open his mouth, just to say something,  _anything_ , when the other man beats him to it.

“Sorry.”

Oikawa’s head snaps up.  

“I am sorry I assume,” Iwa says and Oikawa notes he’s playing with his necklace again. “I just- you looks expectant,  _hopeful_ even _,_  when the train came in. So I just assume…”

“No,” Oikawa says, putting on a (weak, oh so weak) smile as he feels the guilt in his stomach weight even heavier. “Don’t apologize for this… I am just… hoping for the best. For the both of us-” Oikawa swallows- “Maybe we’d both find homes in Paris, won’t we?”

Oikawa curls and (forcefully) uncurls his hands as Iwa gives him the first genuine smile since they’ve met. 

“Yeah,” Iwa says, eyes soft. “Maybe we will.”

 

**Notes for the Chapter:**

> Iwaizumi being referred as Iwa because that’s the name he’s got at the orphanage.
> 
> One of my all-time favorite movie with iwaoi. Hope you like it~
> 
> tumblr: aunnoo-iwaoi-headcanon.tumblr.com (main blog: aunnoo.tumblr.com)


	4. Red String Soulmates: First Encounter

**Summary for the Chapter:**

> Inspired from the soulmates AU prompt -- asked by imaginativeoptimist. 
> 
> Basic ideas before reading it:  
> \- Iwaizumi is born with the ability to see red string of fates around people's little fingers.  
> \- Iwaizumi is now in his third years of college and the captain of their uni volleyball club.  
> \- (Kuroo's the vice captain.)

Hajime stares and almost brings his other hand to rub at his (probably very tired) eyes. 

It isn’t that he has never seen a red string of fate attached to one’s finger (because he does and has been able to do it since forever.) The problem is he has never seen one around  _his_  finger. 

He stares harder, as if it’d disappear under sheer willpower. 

It doesn’t and he nearly gets a heart attack when his vice captain’s voice pipes in. 

“Anything wrong, Iwaizumi? Is the door locked or the handle suddenly caught your interest?”

Hajime shakes his head, more about shaking the illusion out of his sight than giving an answer. 

(The red string is still there.  _Why is it there?_ )

“Nah, just thought I’d seen things.”

Kuroo hums and looks down at Hajime’s hand on the handle. Something must have clicked in his head (which is always dangerous) as Kuroo looks up at Hajime, his signature feline grin plastering all over his features. 

“Ohoho, don’t tell me-”

 _Shit!_ “How did you even-” Hajime says, his hand reaching to cover the other out of instinct before he curses again because he basically confirms whatever conclusion Kuroo has come up in his mind, which is very likely correct since Kuroo is the only person who knows Hajime's… ability. 

“You got yours! Where does it lead to?” Kuroo leans in and stares at Hajime’s covered hand as if he could suddenly develop the ability to see. 

“Nowhere,” Hajime says, refusing to let Kuroo get on the issue even more. “We’ve got a tryout to hold and a bunch of freshmen to handle.”

“Don’t you captain duty me, Iwaizumi,” Kuroo says. “I won’t let you get off the topic that easily.”

“Can we go in already?” Iwaizumi grunts, staring grumpily at his hand on the handle, that red string which has caused all his headache this morning flaunting right back at him mockingly while leading all the way towards…

“You should open the door first, dear captain,” Kuroo says, sly grin going full force again. “Unless there’s certain reason holding you back, like, I don’t know, the first meeting with your fated mate inside the stadium?”

“What are you-”

The door swings open inwards suddenly and Hajime almost falls forwards along with the force. His sense of balance, which has helped him more than once on the court, kicks in and saves his footing. Hajime lets go of his hand and takes a step back to straighten up. His eyes catch something before he could look up. 

The end of his red string, attaching to long, slender,  _masculine_  finger. 

Hajime looks up sharply. He would’ve heard his neck giving a protesting pop sound if he didn’t caught the little gasp from the person before him.

Hajime is caught by a pair of chocolate brown eyes.

It’s a boy, tall(er) and lean, his hair a lighter shade of brown than his eyes. He looks younger, very likely a freshman, and his features are  _exquisite_. If one doesn’t take in his volleyball sportswear and slightly sweaty state, they would claim the boy a model rather than an athlete. 

But now this model-like boy is looking at Hajime like  _Hajime_  is the shining and fascinating one.

“Iwaizumi-senpai,” the boy exclaims, and Hajime swears his mind’s hallucinating again as he sees the boy’s eyes sparkle and his cheeks take on a hue of excited pink. 

The boy extends his hand, his hand that has that supposedly-not-there red string linking to Hajime’s, and flashes Hajime a bright, (blindingly) bright smile.

“It’s so nice to finally meet you, Iwaizumi-senpai,” the boy says. “I am Oikawa Tooru. 

 **I am here to become your new setter.** ”

**Notes for the Chapter:**

> Because we always need more soulmate AU for these dorks. Also that I'd want more touch on senpai/kouhai iwaoi dynamics. 
> 
> Feel free to come and shout about them with me!  
> tumblr: aunnoo-iwaoi-headcanon.tumblr.com (main blog: aunnoo.tumblr.com)


End file.
